Municipal utilities usually bury their mains under public rights of way, such as streets. At spaced intervals throughout the system, normally open shut-off valves are incorporated for the purpose of isolating main breaks so they can be repaired.
The shut-off valves are frequently buried several feet beneath the street and access pipes are provided which extend upwardly from the valve to near street level. The access pipe provides a passage for a tool which can be manipulated from street level to actuate the valve.
A cover with a removable lid is usually incorporated into the street pavement to prevent debris from filling the access pipe. These lids usually have lift openings therein which allow some debris to pass the cover. In addition, vehicle movement and vandalism often cause the lids of these covers to be displaced and even lost. These factors allow debris to enter the access pipe and prevent or delay access to the valve. Time is important in repairing gas and water main breaks and the need to clean out an access pipe can significantly delay such repairs.
U.S. Pat. No. 4,921,123, granted May 1, 1990, to G. J. Mizioch for "DEBRIS CAP" discloses an inexpensive and easily installed debris cap for closing the upper end of an access pipe. That cap employs a cam-actuated slide for wedging the cap in place in the pipe. The cam is manipulated by means of a rotatable handle positioned atop the cap.
The ease of installation and removal of the Mizioch debris cap is both an advantage and a disadvantage. It is very helpful for legitimate installers and removers of the cap. But it also makes it easy for vandals to steal the cap and allow debris to enter the valve access pipe. There continues to be a need for a debris cap which is easily installed and removed by authorized personnel, but which can be locked in position to prevent unauthorized removal.